OP0210 BRUTON’S TYROSINE KINASE (BTK) IS A NOVEL INDEPENDENT BIOMARKER OF LYMPHOMA IN PRIMARY SJÖGREN’S SYNDROME: DATA FROM 346 PATIENTS OF THE ASSESS COHORT
Authors: P. M. Duret, C. Schleiss, N. Sedmak, N. Meyer, T. Ye, L. Kawka, A. Saraux, V. Devauchelle-Pensec, D. Cornec, C. Larroche, A. Perdriger, R. Seror, R. Felten, J. Sibilia, G. Nocturne, X. Mariette, J. E. Gottenberg
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Primary Sjögren's syndrome (pSS) is a B-cell driven systemic auto-immune disease associated with the highest risk of lymphoma among systemic auto-immune diseases. In the prospective ASSESS cohort (395 patients enrolled, with a 10-year follow-up), transcriptomic analysis recently showed the association between baseline peripheral blood overexpression of Bruton's tyrosine kinase (BTK) and lymphoma. <h3>Objectives</h3> This study aimed to confirm the transcriptomic findings at the mRNA and protein level and to evaluate the relevance of BTK as a lymphoma predictor with regards to other predictors. <h3>Methods</h3> BTK mRNA expression was assessed using qRTPCR in whole blood samples from 63 patients (12 patients with a history of lymphoma, 9 patients with incident lymphoma occurring during the 10-year follow-up, 21 patients without lymphoma and no risk factors for lymphoma and 21 patients without lymphoma and ESSDAI ≥ 5). BTK protein expression in peripheral blood was analyzed by flow cytometry in 7 healthy controls, 5 pSS patients without risk factors for lymphoma, 8 pSS patients with ESSDAI ≥5, and 6 pSS patients with lymphoma. In 346 patients of the ASSESS cohort for whom all data were available, the association between pSS-related lymphoma and BTK expression at enrolment, with 9 validated lymphoma predictors (parotid enlargement, purpura, ESSDAI ≥ 5, lymphocytopenia, CD4/CD8 ratio ≤ 0.8, RF positivity, cryoglobulinemia, monoclonal component, and low C4) and other potential biomarkers (serum FLT3L, BAFF, digital interferon alpha, gammaglobulins, IgG, beta2microglobulin, kappa and lambda free light chains, quantitative levels of anti-SSA/SSB) was analyzed. Multivariate analyses took into account in a first model, BTK and the 9 validated predictors of pSS-related lymphoma, and in a second model variables associated with lymphoma in univariate analysis selected by a stepwise procedure. <h3>Results</h3> In qRTPCR, BTK was significantly upregulated between pSS patients with and without lymphoma. In flow cytometry, BTK protein expression in CD19<sup>+</sup> B cells (p=0.03), and in most B-cell subpopulations, was significantly increased in patients with lymphoma compared to healthy controls. A gradual increase was observed in BTK expression of CD19<sup>+</sup> B cells, between patients without risk factors for lymphoma, those with ESSDAI ≥5, and those with lymphoma. In multivariate analysis, taking into account 9 validated predictors of lymphoma in pSS, BTK expression at enrolment was significantly associated with lymphoma (adjusted OR [aOR] 1.45; 95% CI [1.19-1.82]; p&lt;0.001), along with CD4/CD8 ratio ≤ 0.8 (aOR 6.03; 95% CI [1.23-26.13]; p=0.02). In a second model including 4 biomarkers selected by a stepwise procedure, BTK expression remained significantly associated with lymphoma (aOR 1.36; 95% CI [1.14-1.64]; p&lt;0. 001), as well as serum BAFF levels (mean [SD]:1028.5 pg/ml [710.3]; per 1000 BAFF units, aOR 2.04; 95% CI [1.3-3.19]; p=0.001), low C4 (aOR 4.16; 95% CI [1.43-13.88]; p=0.01) and CD4/CD8 ratio ≤0.8 (aOR 10.62; 95% CI [2.49-44.15]; p=0.001). <h3>Conclusion</h3> These results confirm that increased expression of BTK in peripheral blood is associated with pSS-related lymphoma. These results also show the potential interest of combining B-cell (BTK and BAFF) and T-cell (CD4/CD8 ratio)-related biomarkers to evaluate the risk of lymphoma in pSS. <h3>Acknowledgements</h3> To the patients for their participation to the ASSESS cohort; To the investigators of the ASSESS cohort; plateforme de transcriptomique de l'Institut Cochin; centre de ressources biologiques de l'Hôpital Bichat; The French Society of Rheumatology. <h3>Disclosure of Interests</h3> Pierre-Marie DURET: None declared, Cédric Schleiss: None declared, Nathanaël Sedmak: None declared, Nicolas Meyer: None declared, Tao Ye: None declared, Lou Kawka: None declared, Alain Saraux: None declared, Valerie Devauchelle-Pensec: None declared, Divi Cornec: None declared, Claire Larroche: None declared, Aleth Perdriger: None declared, Raphaèle Seror: None declared, Renaud FELTEN: None declared, Jean Sibilia: None declared, Gaetane Nocturne: None declared, Xavier Mariette Consultant of: Astra Zeneca, BMS, Galapagos, GSK, Novartis, Pfizer, Jacques-Eric Gottenberg Consultant of: Astra Zeneca, BMS, Galapagos, GSK, Novartis, Pfizer.